Noise controllable nozzle closure

ABSTRACT

A rocket motor nozzle closure for controlling the initial release of  prese from the rocket motor nozzle to reduce the occurrence of high pressure shock fronts which are detrimental to the weapon operator. The mass and geometry of the nozzle closure are predetermined to fit the desired motor performance. The release of motor pressure is controlled by the rate of change of momentum of the nozzle closure.

BACKGROUND OF THE INVENTION

Rocket motor ignition is normally controlled by utilizing an igniter which gives a controlled rate of heat release which simultaneously pressurizes the motor. Nozzle closures are used to aid ignition by retaining the igniter action until proper motor pressure is obtained. The nozzle closures normally used are metal or plastic and are retained in the nozzle by mechanical design or adhesives. When the desired pressure is reached, the closure is ruptured, sheared,extruded or overcomes the bond strength if adhesive is used. Such method of motor opening can generate an unacceptable noise level.

The present invention relates to nozzle closures which reduce and control the noise level generated by rocket motors during ignition by incrementally or continuously opening the motor.

Such closures are used to reduce the shock wave effect produced internally and externally to the motor. This is particularly advantageous for motors which operate near personnel.

SUMMARY OF THE INVENTION

A nozzle closure for rocket motors that incrementally or continuously opens the nozzle of the motor for controlling the initial release of pressure therefrom. The closure includes a forward portion extending into the motor and an aft portion extending rearwardly into the exit portion of the nozzle. The mass and geometry of both the forward and aft sections are predetermined to control the pressure release by rate of change of momentum of the closure during motor ignition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational sectional view of the present invention. FIG. 2 is an enlarged sectional view of the forward section of the nozzle closure of FIG. 1.

FIGS. 3-6 are elevational sectional view of various configurations of the aft sections of the nozzle closure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, a rocket motor 10 includes a nozzle having a throat 12, an entrance section 14 and an exit section 16. A nozzle closure member 18 is mounted in the nozzle. A typical configuration includes a forward section 20 carried in the entrance section of the nozzle, a central section 22 which configurations range from contours and straight sections of zero to some given length, and an aft section

FIG. 2 illustrates a forward closure member 18 having a substantially cylindrical portion 48, a tapped portion 50 and blunt portion 52. Apertures 53 are provided in the member in communication with the combustion chamber and a hollow portion 56 of the closure member. The vent holes allow some gas to escape prior to expulsion of the closuremember from the nozzle.

FIGS. 3-6 illustrate various configurations of the aft portion 24 of the closure member. In these FIGS. it is seen that the aft portion is provided with various configurations which effect the mass and drag of the aft closure member.

FIGS. 3, 5 and 6 discloses aft sections having substantially frusto conical configurations. Aft portion 24 (FIG. 3) illustrates a solid portion 54. FIG. 5 is provided with a hollowed out portion 56 to provide an aft section which will be of less mass than the solid aft section of FIG. 3. As seen in FIG. 6 a variable mass 58 is incorporated in the aft section. The weight and material of the variable mass is dependent upon the specific motor characteristics. The aft section of FIG. 4 is solid with cylindrical surface 60.

It is to be understood that in the nozzle closures any of the aft sections shown can be combined with any of the forward sections shown. The choice depends on the motor characteristics, it only being required that the nozzle closures produce controlled opening in a predetermined manner. Since such opening is controllable by the overall density, configuration, and overall mass, low density closures can be used to give high motor pressure or vice versa. 

I claim:
 1. In a rocket motor having a nozzle including an entrance section a throat section and an exit section, closure means for controlling the opening of said nozzle responsive to ignition of said rocket motor comprising:a. a forward section disposed in said entrance section of said nozzle, said forward section being provided with a hollow configuration having openings communicating into said motor and the atmosphere; b. an intermediate section disposed in said throat section; and, c. an aft section disposed in said exit section of said nozzle, d. said closure member having a predetermined density and mass for controlling the change of momentum of the closure member responsive to ejection thereof from said nozzle, whereby said nozzle opening is controlled incrementally or continuously.
 2. A nozzle closure as set forth in claim 1 wherein said aft section is provided with a frusto-conical configuration having a cut-out portion in the base thereof. 